The beach at Cape Henlopen State Park was open Tuesday morning, but the no-swimming flag was posted, a day after a teenager was bitten by a shark. / Chuck Snyder, The (Wilmington, Del.) News Journal

by Molly Murray, The (Wilmington, Del.) News Journal

by Molly Murray, The (Wilmington, Del.) News Journal

WILMINGTON, Del. -- A state fisheries biologist confirmed that a 16-year-old Delmar teen was bitten by a shark at Cape Henlopen State Park late Monday afternoon.

State officials reopened the beach for swimming about 1 p.m. Tuesday, after observing the waters from the shore and helicopter.

"We saw plenty of dolphins, cow-nose rays, sturgeon and menhaden, but no sharks," said Collin O'Mara, secretary of the state Department of Natural Resources and Environmental Control. O'Mara and state fisheries biologist Scott Newlin boarded a state police helicopter at the park and flew along the ocean swimming beach and the sandy flats on the Delaware Bay side of Cape Henlopen.

O'Mara said that their observations, along with lifeguards watching from land over several hours, prompted state officials to lift the swimming ban.

"We have taken every precaution," O'Mara said. "All evidence points to it being a completely isolated event."

Sharks are common in Delaware's waters this time of year. But shark attacks are rare. Since 1940, there have been four shark attacks â?? including this one â?? in Delaware waters, according to the database at the University of Florida. The biggest period for shark attacks was in the 1960s, when two were reported in Delaware. During that same time, there were six reported in New Jersey.

One reason for the rarity of attacks, said Dewayne A. Fox, a shark researcher and assistant fisheries professor at Delaware State University, is that sharks target fish for prey. "They don't want anything to do with us," he said.

State fisheries biologist Newlin looked at photos of the youth's injuries and immediately concluded it was a shark bite.

"Based on the bites, I'm thinking it was a juvenile sand bar" shark, Newlin said.

Shortly before lifeguards at the state park went off duty at 5 p.m., the 16-year-old felt something grab his left arm as he stood in 5 to 5 1/2 feet of water, said Wayne D. Kline, state park chief of enforcement.

At the time, the teen was standing in the water, splashing and skimming at the surface with his hands, Kline said.

The teen saw a shark, hit it with his right hand, and the animal swam off.

Newlin said the scrape marks on the teen's right hand are a sign of a shark because their skin is rough and can cause abrasions.

Sand bar sharks once supported almost 70 percent of the entire East Coast commercial shark fishery, Fox said. The population declined, and the species is now protected to allow it to rebound.

Newlin estimates the shark was young and probably no more than 3 feet to 4 feet longer, anything larger, and the teen's injuries would have been more significant.

The wound was significant enough that the teen received nearly two dozen stitches at Beebe Healthcare's hospital in Lewes.

On Facebook, the teen, who identified himself as Andrew Vance, posted pictures of the wound and said he had received 23 stitches and the injury was painful.